The Collaborative International Dictionary of English v.0.48:

Orthodox \Or"tho*dox\, a. [L. orthodoxus, Gr. 'orqo`doxos;
   'orqo`s right, true + do`xa opinion, dokei^n to think, seem;
   cf. F. orthodoxe. See Ortho-, Dogma.]
   1. Sound in opinion or doctrine, especially in religious
      doctrine; hence, holding the Christian faith; believing
      the doctrines taught in the Scriptures; -- opposed to
      heretical and heterodox; as, an orthodox Christian.
      [1913 Webster]

   2. According or congruous with the doctrines of Scripture,
      the creed of a church, the decree of a council, or the
      like; as, an orthodox opinion, book, etc.
      [1913 Webster]

   3. Adhering to generally approved doctrine or practices;
      conventional. Opposed to unorthodox.
      [1913 Webster +PJC]

            He saluted me on both cheeks in the orthodox manner.
                                                  --H. R.
                                                  Haweis.
      [1913 Webster]

   4. Of or pertaining to the churches of the Eastern Christian
      rite, especially the Greek Orthodox or Russian Orthodox
      churches, which do not recognize the supremacy of the Pope
      of Rome in matters of faith.
      [PJC]

   Note: The term orthodox differs in its use among the various
         Christian communions. The Greek Church styles itself
         the "Holy Orthodox Apostolic Church," regarding all
         other bodies of Christians as more or less heterodox.
         The Roman Catholic Church regards the Protestant
         churches as heterodox in many points. In the United
         States the term orthodox is frequently used with
         reference to divergent views on the doctrine of the
         Trinity. Thus it has been common to speak of the
         Trinitarian Congregational churches in distinction from
         the Unitarian, as Orthodox.` The name is also applied
         to the conservative, in distinction from the "liberal",
         or Hicksite, body in the Society of Friends.
         --Schaff-Herzog Encyc.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Orthodox
    adj 1: of or pertaining to or characteristic of Judaism;
           "Orthodox Judaism" [syn: Orthodox, Jewish-Orthodox]
    2: adhering to what is commonly accepted; "an orthodox view of
       the world" [ant: unorthodox]
    3: of or relating to or characteristic of the Eastern Orthodox
       Church [syn: Orthodox, Eastern Orthodox, Russian
       Orthodox, Greek Orthodox]

Moby Thesaurus II by Grady Ward, 1.0:

121 Moby Thesaurus words for "orthodox":
   Christian, Orthodox Jew, Sunni Muslim, accepted, accordant,
   accustomed, acknowledged, admitted, anal, approved, authentic,
   authoritative, authorized, being done, bourgeois, button-down,
   canonical, canonist, comme il faut, common, compulsive, concordant,
   conformable, conformist, conservative, conventional, correct,
   corresponding, customary, de rigueur, decent, decorous, die-hard,
   doctrinal, dour, established, evangelical, faithful, firm, fogyish,
   formal, formalistic, fundamentalist, hard, harmonious, hidebound,
   impliable, in accord, in keeping, in line, in step, inexorable,
   inflexible, iron, ironbound, ironclad, ironhanded, kosher, literal,
   meet, muscle-bound, obdurate, obstinate, of the faith, official,
   old-line, ordinary, orthodox Christian, orthodoxical, orthodoxist,
   pedantic, plastic, popular, precisianistic, prevailing, prevalent,
   procrustean, proper, purist, puristic, puritan, puritanic,
   reactionary, received, recognized, regular, relentless, right,
   rigid, rigorist, rigoristic, rigorous, rockbound, sanctioned,
   scriptural, seemly, sound, square, standard, stiff, straight,
   straightlaced, straitlaced, stubborn, stuffy, textual, textualist,
   textuary, the orthodox, tory, traditional, traditionalist,
   traditionalistic, true, true believer, true-blue, unbending,
   uncompromising, unrelenting, unyielding, uptight



The Devil's Dictionary (1881-1906):

ORTHODOX, n.  An ox wearing the popular religious joke.